Methods and devices for handling radioactive waste in different types of nuclear installations are well-known. One way of taking care of a first compound, for example radioactive waste, is to mix it by stirring it with a second compound, for example cement powder, so as to form a mixture and to allow the mixture to solidify in a container, for example an ultimate waste disposal container. The container has an edge forming an opening at one end. A stirrer is arranged in the container for stirring the mixture in the container. A drive means is connected to the stirrer through the opening of the container while the mixture is being stirred. After the mixture has been stirred, the container is sealed by a lid and the stirrer remains in the container.
The problem is that, upon rotation of the stirrer in the container, a wave is generated which results in the mixture overflowing the edge of the container. To avoid overflow, the container is only filled to a certain level below the edge. This method results in a void being created in the upper part of the container, whereby the volume of the container upon ultimate waste disposal is not utilized in full.
One method for preventing the mixture in the container from overflowing during stirring is to arrange a lid over the opening of the container. The disadvantage of this method is that the wave which is generated during rotation of the stirrer contacts, through hydrodynamic forces, to the underside of the lid and thus disturbs process of the stirring.
A further disadvantage is that the lid after having been in contact with the mixture in the container is polluted and must be cleaned or taken care of. Cleaning entails costs or may be complicated, as in the case of, for example, radioactive pollution.
It is an object of the invention to provide a method and a device in which the volume of the container is utilized more efficiently as compared with the prior art.
A further object is to prevent the mixture contained in the container from overflowing the open edge of the container.
An additional object is to dispose of the device which is polluted by the mixture.